Implicit Conversions

An implicit conversion from type S to type T is defined by an implicit value which has function type S => T, or by an implicit method convertible to a value of that type.

Implicit conversions are applied in two situations:

  • If an expression e is of type S, and S does not conform to the expression’s expected type T.
  • In a selection e.m with e of type S, if the selector m does not denote a member of S.

In the first case, a conversion c is searched for which is applicable to e and whose result type conforms to T. In the second case, a conversion c is searched for which is applicable to e and whose result contains a member named m.

If an implicit method List[A] => Ordered[List[A] ] is in scope, as well as an implicit method Int => Ordered[Int], the following operation on the two lists of type List[Int] is legal:

List(1, 2, 3) <= List(4, 5)

An implicit method Int => Ordered[Int] is provided automatically through scala.Predef.intWrapper. An example of an implicit method List[A] => Ordered[List[A = new Ordered[List[A

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Implicit conversion